Technical Manual
13
CALIBRATION TESTING
The Calibration Key provides a convenient means of testing the thermometer for accuracy.
Calibration Key Procedure
1. Extract the probe and disconnect it from the thermometer.
2. Insert the Calibration Key into the probe connector receptacle on the thermometer and observe
the display. The display should read CAL for two seconds, and then go blank.
3. Insert a probe shaft into the probe storage well and remove it to initiate a temperature taking cycle.
Wait for the display test and then observe the display. The display must read between 97.1°F(36.2°C)
and 97.5°F(36.4°C) inclusive for the calibration of the instrument to be correct.
4. Remove the Calibration Key and reinstall the probe connector plug.
5. Then install the probe into the probe storage well.
Note: The Calibration Key test does not test the probe. To do so requires the use of the
Welch Allyn Model 9600 Calibration Tester.
If the reading from the Calibration Key is not within the specified range or you are having other
problems with the use of the Calibration Key, refer to the Troubleshooting section.
M9600 Procedure
The Model 9600 Calibration Tester provides a convenient means of testing the entire thermometer
system (instrument and probe).
· The 9600 Calibration Tester must be warmed up and stable at one of the two available
temperature settings.
· The unit under test must be in Monitor mode with no probe cover loaded onto the probe.
The probe is inserted into the small hole in the dry heat well of the 9600 Calibration Tester and
allowed to settle for a minimum of 2 minutes to the final temperature. The reading on the
thermometer must be within the range specified on the 9600 Calibration Tester. Refer to the Model
9600 Calibration Tester Operation Manual for complete instructions.
Note: All Welch Allyn and Diatek thermometers (thermistor and infrared ear thermometers)
can be checked in the Model 9600.
If you are having problems with the use of the Model 9600, refer to the Troubleshooting section in
the Model 9600 Operation Manual.
THEORY OF OPERATION
This section describes in detail the operation of the various subcircuits in the M767 Thermometer.
Refer to Figure 3 for a block diagram representation of the circuits and Figure 6 for the circuit
schematic.
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